Trypanosoma cruzi, a parasitic protozoan, is the causative agent of Chagas' disease, a multisystemic disorder that affects millions of people in Latin America. T. cruzi exists in three distinct developmental forms: epimastigotes, which multiply extracellularly in the midgut of reduviid bugs; amastigotes, which multiply inside mammalian cells; and trypomastigotes, which transmit infection from insects to man and vice-versa, but which do not multiply.
Trypomastigotes must travel through the bloodstream, cross the vascular epithelium, and migrate through the extracellular matrix to reach the cells of the organs which T. cruzi infects. Once they have entered host cells, trypomastigotes transform into amastigotes which multiply and eventually transform back into trypomastigotes which can exit the host cell and migrate through the interstitial tissue to invade other cells.
Receptor-ligand interactions may play a role in T. cruzi invasion of cells. Ouaissi et al. (Science 234:603, 1986) report that peptides modeled on a protein, fibronectin, present on host cells can inhibit T. cruzi infection in vitro. Ouaissi et al. (Mol. and Biochem. Parasitol. 19:201, 1986) report the identification and isolation 80-85 kD trypomastigote cell surface protein with properties expected of a fibronectin receptor. Velge et al. (Parasitology 97:255, 1988) report the isolation of a T. Cruzi trypomastigote collagen-binding protein. When analyzed by polyacrylamide gel electrophoresis, the protein migrates as a 58 kD protein under non-reducing conditions and as a 68 kD protein under reducing conditions. Velge et al. also identify an 80-85 kD protein which reacts with antibodies raised against the 68/58 kD protein; they suggest that both the 80-85 kD and the 58/68 kD glycoproteins form part of the same receptor.